The long-term objective of this proposal is to develop an antisense delivery system passively targeted to solid tumors via the EPR effect. Our stepwise approach is as follows: (1) Ligand design and synthesis: The ligand is a double stranded oligonucleotide heteroduptex comprising a nuclease-resistant antisense agent and a partially complementary DNA "carrier" strand terminally derivatized with antigenic epitopes for antibody binding. Two features must be emphasized: (i) the intrinsic rigidity of dsDNA makes this ligand functionally bivalent with respect to IgG binding, and (ii) partial strand complementarity allows for strand thermal dissociation when heated. (2) Antibody binding optimization: The effect of antigen valence and epitope density on the affinity/avidity of specific antibodies will be tested using isothermal titration calorimetry. The duplex exhibiting the greatest affinity for the antibody will be chosen for further characterization. (3) Antisense design and in vitro model development: the antisense effect of a 17-mer oligomer directed against a point mutation in the murine H-Ras oncogene will be evaluated in a DMBA/TPA transformed BALB/MK-2 keratinocyte cell line. Indicators of oncogene downregulation are c-Ha-Ras mRNA levels and p21 (H-ras gene product) expression. (4) In vivo model development: The pharmacokinetic and pharmacodynamic advantage of this delivery system will be tested in antigen-immunized, DMBA/TPA treated, SENCARB/PtJ mice.